Passive Q-switched erbium-doped fibre laser with saturable absorber

In this paper, we report that a passive Q-switched erbium-doped fibre laser can be constructed by inserting a segment of samarium-doped fibre into the ring cavity as saturable absorber. Our result shows that when the erbium-d oped fibre has a large gain coefficient and the samarium-doped fibre has su fficient absorption, self-pulsing can readily be obtained. Furthermore, if the saturable absorber has large transition cross section, narrow Q-switche d pulses of very large amplitude are produced. (C) 1999 Elsevier Science B. V. All rights reserved.